Noise attenuation valves are often used in vehicle exhaust systems to reduce noise generated during vehicle operation. A noise attenuation valve typically includes a flapper valve mounted on a shaft that pivots the flapper valve within an inlet tube formed within an exhaust component, such as a muffler for example. The flapper valve has a disc shaped body that rotates within the inlet tube to vary exhaust gas flow area. The shaft is coupled to a solenoid with a linkage assembly. A controller controls the solenoid to rotate the shaft via the linkage assembly. As the shaft rotates, the flapper valve varies the exhaust gas flow area as needed to attenuate noise.
One disadvantage with this traditional configuration is that components in the noise attenuation valve and solenoid generate operational noise. For example, movement of the linkage assembly and rotation of the shaft can generate noises due to slack and clearance between the components.
Additionally, operational movement of the solenoid generates undesired noise. The solenoid includes a plunger that is coupled to the linkage assembly. When the solenoid is electrically actuated, an electronic voltage is used to generate a magnetic force that pulls the plunger in a first direction to position the flapper valve at a desired position. The plunger can move until a travel limit stop is reached. The velocity at which the plunger moves, and the force at which the travel limit stop is contacted, can generate undesirable noise. Further, when the electronic voltage is cut-off, a spring forces the plunger in a second direction, opposite of the first direction, to return the flapper valve to an initial position. This quick release of the plunger also generates undesirable noise and increases wear rates of associated exhaust valve components.
Thus, it is desirable to provide a method and apparatus for controlling movement of the actuator for an exhaust valve that reduces operational noises and reduces wear rates.